May 14, 1917 
Soil Nitrogen and'Nutrition of Citrus Plants 
241 
sampling tube to the desired depth and then drive under a thin iron 
plate to prevent the soil from falling out as the tube was removed. 
On August 9 five successive sets of 12 samples each were drawn from 
a strip of soil 2 inches wide, 48 inches long, and 15 inches deep. The 
nitric nitrogen as determined in each sample is shown in Table XXVII. 
The upper 3 inches of soil showed an average nitrate content of 0.70 mgm. 
In the second 3-inch section the average is only 0.19 mgm., with the 
variation in individual samples from 0.08 to 0.25 mgm. The soil at a 
depth of 6 to 9 inches shows an average nitrate content of only 0.14 
mgm., with a variation in individual samples from 0.05 to 0.29 mgm. 
The fourth and fifth sections show a higher nitrate content than the 
second or third. 
, Table XXVII .—Distribution of nitrates in soils at Covina , Cal ., irrigated by an overhead 
system of irrigation . Season of igi6 
[Results expressed as milligrams of nitrogen per ioo gm..of soil] 
Date of 
sampling. 
Depth. 
Boring No. 
Aver¬ 
age. 
1 
2 
3 
4 
S, 
6 
7 
8 
9 
10 
IX 
12 
Aug. 9. 
Au'g. 30 (be¬ 
fore irri¬ 
gation)... 
Sept. 2 (af¬ 
ter irri¬ 
gation) ... 
Inches . 
0- 3 
3 - 6 
• 6 - 9 
9-12 
12-15 
0- 3 
3 “ 6 
6 - 9 
9-12 
12-24 
24-736 
36-48 
0- 3 
3 - 6 
6 - 9 
9-12 
' 12-24 
24-36 
36-48 
48-60 
0.64 
.19 
• 05 
. 22 
.19 
i. 16 
•36 
*32 
•IS 
0. 71 
• IS 
. 12 
•IS 
. 26 
1-37 
. 22 
•25 
•IS 
O.71 
•IS 
•IS 
.29 
. 22 
1.30 
. 22 
. 18 
■•IS 
0. 5 © 
. 22 
. 12 
.29 
.29 
1.30 
•25 
. 22 
•15 
0.92 
.08 
.IS 
• 36 
.29 
•74 
•39 
. 22 
•25 
0.64 
.25 
•IS 
. 22 
. 22 
•67 
•39 
•39 
•32 
0.64 
. 22 
•IS 
. 26 
.29 
.88 
•39 
•74 
.46 
o- 20 
•15 
. 12 
.29 
. 26 
.88 
•25 
•36 
. 22 
0. 78 
. 22 
.08 
• 15 
• 19 
•95 
•29 
•36 
•39 
0-57 
.19 
.29 
•15 
.29 
1.06 
•53 
.32 
•25 
0 
M»M*0 M H H l/l 
0. So 
. 22 
•15 
•15 
.22 
.88 
' . 22 
.18 
•15 
0.70 
•19 
• 14 
.22 
•25 
z. 01 
• 31 
•31 
•23 
•IS 
.18 
• 32 
•55 
•56 
•57 
•75 
.92 
•32 
.18 
.08 
•43 
•36 
•36 
.46 
•39 
1.16 
•29 
.50 
•S 3 
•95 
•S 3 
.64 
.60 
.46 
.67 
1.44 
•S 3 
.64 
•74 
• 95 
.60 
.29 
•95 
i -13 
•57 
•39 
• 67 
.60 
.46 
.46 
. 60 
•39 
1.02 
•39 
.46 
. 81 
•39 
•50 
.46 
•57 
. 
1 
| 
1 
In this series of samples it is seen that the lateral distribution of the 
nitrates is quite uniform, but that there is some tendency for the nitrate 
to accumulate in the surface 3 inches even under an overhead system of 
irrigation. 
In order to study more exactly the effect of overhead irrigation on the 
distribution of nitric nitrogen, two additional sets of samples were taken, 
one on August 30 just before the irrigation and the other on September 2 
after an application of about 3 inches of water. On August 30 the aver¬ 
age nitric-nitrogen content in the upper 3 inches was 1.01 mgm., which was 
more than the total amount found in the next three sections. On Sep¬ 
tember 2 the highest nitrate content was found at a depth of 12 to 24 
inches, while the surface 3 inches contained the smallest amount found in 
the upper 2 feet, The figures presented in Tables XXVI and XXVII 
would seem to leave little doubt that the overhead irrigation gives a 
much better distribution of nitric nitrogen than can be secured under the 
